Switch device



F. A. HESTER SWITCH DEVICE June 11, 1946.

Filed Dec. 30, 1944 WHTEE IN V EN TOR. FRHNK Hw HESTER BY A ITTORNEY [0005776 to P2515?! (Dyna/M70 15 rnsod cy g ap Patented June 11, 1946 SWITCH DEVICE Frank A. Hester, New York, N. '31., assignor to Radio Corporation of America, a corporation of Delaware Application December 30, 1914, Serial No. 570,575

13 -Claims. 1

This invention relates to electric switch devices, and more particularly to an inertia typ switch operable in response to acoustic energy, the present invention being especially suited for use under water, although by no means limited thereto.

There are many devices employed in naval activities in connection with which electriccircuits are used. For example, mines are placed in harbors or at other strategic points to be set on by a detonating device connected in a suitable electric control circuit which is to be rendered operative when a ship is within certain range of the mine. In such a circuit, an acoustically responsive switch which is rendered operative to close the circuit by sonic waves produced by the passing vessel is very useful. Again, a switch of this sort may be connected in an electric circuit which is arranged to operate a suitable signal or alarm system on shore instead of in a mine detonating system. Many other uses are also found for acoustically responsive switches. Thus, for example, this type of switch may be used in a control circuit for opening a garage door, the switch being rendered operative when, with the car in front of the door, the horn is blown to provide the necessary acoustic energy. There are also uses for inertia type electric switches where the actuating source is not necessarily an acoustic wave but any, mechanical disturbance or vibration. Thus, a switch of the type constituting my present invention may be mounted inside of a safe and rendered operative to complete an alarm circuit when an unauthorized person tam 'pers with the safe by tapping it or by taking any other action which will produce mechanical vibrations of sufficient magnitude.

The primary object of my present invention, therefore, is to provide an improved inertia type electric switch which will be rendered operative by acoustical or by mechanical vibrations.

More particularly, it is an object of my present invention to provide an electric switch as aforesaid which ls especially useful under water and which can be actuated by acoustic or sonic waves set up therein.

Another object of my present invention is to provide an inertia type electric switch as above set forth which is extremely sensitive and which can be set or adjusted readily for the required degree of sensitivity. i

Still another and important object of my present invention is to provide an improved. inertia typeelectric switch which avoids the use of bat- 2 teries or other external sources of power for its successful operation.

A further object of my present invention is to provide an improved inertia type electric switch as aforesaid which isresponsive to extremely small amounts of acoustic energy, particularly in the form of random sound of relatively low frequency, and which will obtain the necessary power for its operation solely from the sound field itself.

It is also an object of my present invention to provide an improved electric switch as above .set forth which is simple in construction, economi cal in cost, and highly efdcient in use.

In accordance with my present invention, the switch mechanism consists essentially of three vibrating systems each of which is tightly coupled to the one preceding it and; all of which are tuned to resonate at substantially the same relatively low frequency (approximately cycles per sec ond). The first system may be composed of a vibratory diaphragm to the center of which is rigidly fastened a first mass which is tuned with the diaphragm to the resonant frequency. Suitable backing members behind the diaphragm and the mass restrain this first vibrating system from excessive motion or vibration. Secured to the above mentioned mass is a second vibratory system comprising a leaf spring or other suitable vibratory reed to which is secured a second mass, this first reed and its associated mass being also tuned to substantially the resonant frequency of the system. The third vibrating system comprises asecond reed which may or may not have secured thereto a third mass and which, in any case, is also tuned to the resonant frequency. This second reed constitutes one contact element of the switch and cooperates with a second contact element in proximity thereto. The diaphragm, the first reed and the second reed are all of different stiffness, the diaphragm being the stiifest'of the three, the first reed having an intermediate stiifness, and the second reed being the least stiff. These three' vibratory members are so related to each other that, upon vibration of the diaphragm at the resonant frequency with relatively small amplitude, the first reed will be vibrated thereby at the same frequency but with greater amplitude, and the second reed will also be vibrated at the same frequency but with still greater amplitude to be brought into engagement with the second contact element to thereby close the switch.

For use in under-water or submarine systems, all partsexcept the diaphragm may be housed 3 within a suitable casing which has openings at both ends. The diaphragm is tightly clamped against the front of the casing to close the opening at this end and to be exposed to the water.

A normally air-filled, collapsible member is mounted behind the other opening of the casing to provide a chamber in communication with the space within the casing. When the switch device is submerged in the water, the pressure of the water causes the collapsible member to collapse partly and force the air therein into the space within the casing, thereby balancing the air pressure on the rear or inner face of the diaphragm against the water pressure on the front or outer face thereof. Consequently, the relation between the vibratory parts of the switch remains the same under water as in the air. A suitable perforated guard member may be placed across the opening in the casing behind which the ccllapsible member is secured to prevent entry of the collapsible member into the aforesaid space upon complete collapse of the collapsible member thereby preventing fouling of the switch.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description of one embodiment thereof, when read in connection with the accompanying drawing, in which Figure 1 is a front elevation of one form of switch device according to my present invention.

Figure 2 is a fragmentary sectional view thereof taken on the lin II- II of Figure 1,

Figure 3 is a sectional view taken on the line III-III of Figure 1,

Figure 4 is a wiring diagram of an electric circuit equivalent to the mechanical system employing my improved switch in the form shown in Figures 1 to 3, and

Figure 5 is a typical sensitivity curve for my improved switch. 7

Referring more particularly to the drawing, wherein similar reference characters designate corresponding parts throughout, there is shown,

in Figures 1 to 3, a pair of easing parts I' and 3.

connected in water tight relation and enclosing a space 5 therein. The front casing part i includes a radially inwardly extending portion la formed with an opening 1, and the rear casing part 3 is provided with a radially inwardly extending portion 3a provided with an opening 8. The parts In and 3a serve as vibration limiting plates, as will be more fully described hereinafter.

Connected across the front end of the calf I part i and tightly clamped against it in watertight relation thereto with the aid of a clamping ring 8 is a vibratory diaphragm ii of phosphor bronze or any other suitable, relatively stifi material. 'Iightly secured to the diaphragm ii at its center is a substantially U-shaped block i3 which extends through the opening 1 and constitutes a mass which is tuned with the diaphragm II to resonate at a suitable low frequency (for example, approximately 150 cycles per second), The mass or block l3 and the diaphragm ii constitute th first of the three vibrating systems of the switch.

Tightly connected to one of the legs of the block I3 is a flat, phosphor bronze leaf spring or other suitable vibratory reed i5 of lesser stiffness than that of the diaphragm I I. The spring or reed ll extends into the space 5 between the legs of the block I! and has one end freely suspended in tnisspace, as clearly seen in'i igure 2. A second, substantially U-shaped block ii of smaller mass than that of the block I3 is secured to the freely suspended end of the reed i5 and is tuned therewith to substantially the same resonant frequency as that of the diaphragm II and its mass I3, namely, about 150 cycles per second. The block or mass l1 extends in a direction generally at right angles to the reed i5 and the block I! and has tightly secured to one of its legs a second vibratory reed i5, which may also be of phosphor bronze or the like and, in one modification, was made of phosphor bronze wire. The reed i9 has the least stiffness of the three vibratory members ii, is and i9 and may or may not have a mass secured thereto (being shown without such a mass in the present modification). The reed It is also tuned to the resc-iriant frequency of the system, or approximately 150 cycles per second. The iJ-blocl; l1 has also mounted thereon, in insulated relation thereto. a terminal plate II which carries an adjustable screw23 in the path of movement of the freely suspended end of the reed IS, the reed i9 and the screw 23 constituting the two contact elements of the switch. A pair of leads II are brought out from the block i9 and the terminal plate 2| through a radial passage 25 in the casing part 3 and a watentight coupling 21 for suitable connection of the switch to an external circuit.

As described above, the diaphragm ii and the block i3 constitute one of the three vibrating systems of the switch mechanism, the leaf spring or reed I5 and its block or mass II constitute the second vibrating system, and the reed i8 constitutes the third of the vibrating systems, the latter two vibrating systems being preferably of the type disclosed and claimed in my copending application, Serial No. 569,521, filed December 23, 1944. The relative stiffness of the three resilient, vibratory members ll, i5 and I9 is such that, when the diaphragm ii is set into vibration at the resonant frequency with relatively small amplitude, the reed IE will vibrate at this frequency with greater amplitude, and the reed IE will also vibrate at this frequency but with still greater amplitude sufficient to bring it into engagement with the terminal screw 23 to thereby close the switch. The terminal screw 23 may be adjusted to vary the spacing between it and the reed i9 to any desired extent, and thus the sensitivity of the switch may be, controlled. The casing portions la and 3a, respectively, back up the diaphragm i i and the block [3 to restrain them from excessive motion. This will prevent the switch mechanism from becoming damaged by an abnormally loud acoustic signal in the vicinity of the switch, such as that resulting from the explosion of a neighboring mine.

When a switch such as described above is lowered into the water, the pressure of the water against the front face of the diaphragm would normally force the diaphragm back toward the backing plate its and would even render the switch inoperative should the switch be lowered to a depth where the water pressure is great enough to actually force the diaphragm against the backing plate la and hold it there. This can be avoided and at the same time, the same relation of the parts of the vibratory system retained under water as in the air by placing oven the opening 8 a collapsible member 29, such as a soft, rubber bulb, preferably housed within a rigid housing 3| which has water-tight coupling with the casing part 8. One or more passages 33 formed in the casing part 3 provide access from the exterior into the space 35 between the collapsible member 29 and'the housing 3|. Thus, when the switch device is submerged, the water rushes in through the passages 33, fills the space 35 and causes the member 29 to collapse more or less, depending upon the depth to which the device is submerged. In turn, the collapsed member 29 forces into the space 5 the air or other gas in the chamber 29a enclosed thereby, thus balancing the air pressure on the inside surface of the diaphragm ll against the water pressure on the outside surface thereof. A perforated guard plate 3"! is placed across the opening 8 to prevent excessive water pressure from entirely collapsing the bulb 29 and forcing it into the space 5 where it would interfere with the operation of the switch.

Figure 4 shows a wiring diagram of the electrlcal analogue of the system comprising the water coupled to the acoustic switch of my pres ent invention, the portion to the left of the line A-A representing the water and the portion to the right of the line A-A representing the acoustic switch. In this wiring diagram,

The voltage E represents the pressure of the acoustic waves onthe diaphragm H,

The resistor Rw represents the resistance of the water load on the diaphragm H,

The inductor MW represents the mass of the water load on the diaphragm II,

The inductor M1 represents the effective mass of the diaphragm H and the block l3, The capacitor C1 represents the compliance of the diaphragm H, The capacitor C2 represents the compliance of the flat spring or reed 15,

The inductor M2 represents the effective mass of thereed or spring l5 and the block H,

The capacitor 03 represents the compliance of the reed i9,

The inductor M3 represents the effective mass of the reed i9, and

The resistor R3 represents the resistance of the reed l9.

It will be noted that the electrical system of Fig. 4 includes three loops which correspond to the three vibratory systems of my improved switch, the loop I corresponding to the diaphragm ii and the mass H, the loop 2 corresponding to the spring reed i5 and the mass I7, and the loop 3 corresponding to the reed I9 and its mass.

The acoustic switch is so designed that it acts as a transformer between the loop I, which has a high impedance substantially the same as the impedance of the water whereby to obtain good matching to the water, and the loop 3, which has a low impedance, By properly matching these impedances, maximum transfer of energy from the water to the final reed i9 is obtained. Figure 5 shows a typical sensitivity curve for my im-=, proved switch.

Although I have shown and described but a single embodiment of the present invention,-it will undoubtedly be apparent to those skilled in the art that various other modifications thereof, as well as changes in the particular one described he ein are possible. I therefore desire that my invention shall not be limited except insofar as is made necessary by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. An inertia switch device comprising a vibratory diaphragm tuned to a predetermined resonant frequency, a first vibratory reed supported thereby and tuned to substantially the same frequency, a second vibratory reed supported by said first reed and also tuned to substantially the same frequency, said second reed constituting one contact element of said switch, and a second contact element cooperatively associated with said second reed, said diaphragm and said two reeds being so related to-each other that upon vibration of said diaphragm at substantially said frequency with relatively small amplitude, said first and second reeds will be caused to vibrate thereby at substantially said frequency with successively greater amplitudes and said second reed will be brought into engagement with said second contact element to close said switch.

2. An inertia switch device according to claim 1 characterized in that said diaphragm and said two reeds are constituted by resilient members of different degrees of stiffness, said diaphragm having the greatest stiffness, said first reed having an intermediate stiffness, and said second reed having the least stiffness.

3. An inertia switch device according to claim 1 characterized by the addition of means cooperatively associated with said diaphragm for limiting the amplitude of vibration thereof.

t. An inertia switch device comprising a vibratory diaphragm, a first mass carried thereby and tuned therewith to a predetermined frequency, a first vibratory reed carried by said first mass, a second mass carried by said reed and tuned with said reed to substantially the same frequency, a

being so related to one another that upon vibration of said diaphragm at substantially said frequency with relatively small amplitude, said first and second reeds will be caused to vibrate thereby at substantially said frequency with successively greater amplitudes and said second reed will be brought into engagementwith said sec ond contact element to close said switch.

5. An inertia switch device according to claim 4 characterized by the addition of means cooperatively associated with each of said diaphragm and said first mass for limiting the amplitude of vibration thereof.

6. An inertia switch device according to claim 4 characterized by the addition of a supporting member for said diaphragm, and characterized further in that the couplings between (1) said diaphragm and said supporting member, (2) said first mass and said diaphragm, and (3) said first reed and said first mass are all very tight.

7. An inertia switch device according to claim 4 characterized in that said diaphragm and said two reeds are constituted by resilient members of different degrees of stiffness, saiddiaphragm having the greatest stiffness, said first reed having an intermediate stiffness, and said second reed having the least stiffness.

8. An inertia switch device according to claim 4 characterized in that said diaphragm and said two reeds are constituted by resilient members of different degrees of stiffness, said diaphragm having the greatest stiffness, said first reed having an intermediate stiffness, said second reed having the least stiffness, and characterized still further by the addition of means cooperatively associated with each of said diaphragm and said first mass for limiting the amplitude of vibration thereof.

9. An inertia switch device according to claim 4 characterized in that said first mass comprises a substantially U-shaped block, characterized further in that said first reed has one end thereof secured to one leg of said block and extend into the space between the legs of said block, the other end of said first reed being freely suspended in said space, characterized further in that said second mass also comprises a substantially U- shaped member the cross arm of which is secured to said freely suspended end of said first reed, and characterized still further in that said second reed is secured to one leg of said member and said second contact element is secured to the other leg of said member.

10. An inertia switch device according to claim 4 characterized in that said first mass comprises a substantially U-shaped block, characterized further in that said first reed has one end thereof secured to one leg of said block and extends into the space between the legs of said block, the other end of said first reed being freely suspended in said space for vibratory movement, characterized further in that said second mass also comprises a substantially U-shaped member which extends at right angles to said first reed, the cross arm of said member being secured to said freely suspended end of said first reed, and characterized still further in that said second reed is secured to one leg of said member and said second contact element is secured to the. other leg or said member.

11. An inertia switch device according to claim 4 characterized in that said first mass comprises a substantially U -shaped block, characterized further in that said first reed has one end thereof secured to one leg of said block and extends into the space between the legs of said block, the other end of said first reed being freely suspended in said space for vibratory movement, characterized further in that said second mass also comprises a substantially U-shaped member which extends at right angles to said first reed, the cross arm of further in that said second reed has one end secured to one leg 0! said member and extends into the space between the legs of said member, the other end of said second reed being freely suspended in said last named space for vibratory movement, and characterized still further in that said second contact element is mounted on the other leg of said member and is disposed in the path of vibratory movement of said freely suspended end of said second reed.

12. A submarine inertia switch device comprising a casing having two openings therein and enclosing a space, a vibratory diaphragm closing one of said openings, said diaphragm being tuned to substantially a predetermined resonant frequency, a first vibratory reed supported by said diaphragm and also tuned to substantially the same frequency, a second vibratory reed supported by said first reed and also tuned to substantially the same frequency, said second reed constituting one contact element of said switch, a second contact element cooperatively associated with said second reed, said diaphragm and said two reeds being so related to each other that upon vibration of said diaphragm at substantially said frequency with relatively small amplitude, said first and second reeds will be caused to vibrate at substantially said frequency with successively greater amplitudes and said second reed "will be brought into engagement with said second contact element to close said switch, said two reeds and said second contact element being disposed in said space, and a normally expanded, gas-fiiied, collapsible member over the other of said openings providing a chamber in communication with said space, said member being collapsible in response to waterpressure when said device is submerged in the water to force the gas therein into said space whereby to increase said member being secured to said freely suspended end of said first reed, characterized still phragm for balancing the water pressure outer face of said diaphragm.

13. A submarine switch device according to claim 12 characterized by the addition of a guard member extending across said second opening for preventing entry of said collapsible member into said space.

on the FRANK A. HESTER. 

